Real Time Diagnostics For Flow Controller Systems and Methods

ABSTRACT

A device that includes a flow controller system that comprises one or more sensors, a flow measurement sensor that comprises one or more sensors. The flow measurement sensor is configured to generate a signal based on determine the difference between the flow as measured by the flow controller system and the flow measurement system in real time.

RELATED APPLICATIONS

This application is a continuation of U.S Utility application Ser. No.14/210,113 filed on Mar. 13, 2014 entitled “REAL TIME DIAGNOSTICS FORFLOW CONTROLLER SYSTEMS AND METHODS”, which is incorporated herein byreference in its entirety. This application also claims benefit fromU.S. Provisional Patent Application No. 61/792,493, filed Mar. 15, 2013,entitled “REAL TIME DIAGNOSTICS FOR FLOW CONTROLLER SYSTEMS ANDMETHODS”, which is incorporated herein by reference in its entirety.

BACKGROUND

The present disclosure relates to the field of flow controllers. Thepresent disclosure relates more specifically to a mass flow controller(MFC) systems and methods for controlling the MFC to control and delivergases, fluids or a combination thereof.

SUMMARY

Various embodiments include a flow controller system that comprises oneor more sensors, a flow measurement sensor that comprises one or moresensors. The flow measurement sensor is configured to generate a signalbased on determine the difference between the flow as measured by theflow controller system and the flow measurement system in real time.

Alternative embodiments relate to other features and combinations offeatures as may be generally recited in the claims. Embodimentsdescribed below allow parallel or serial processing of each methodand/or component.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingfigures, wherein like reference numerals refer to like elements, inwhich:

FIG. 1 is a schematic diagram of a flow delivery system, according to anexemplary embodiment.

FIG. 2a is a schematic diagram of a flow delivery system, according toan exemplary embodiment.

FIG. 2b is a schematic diagram of a flow delivery system, according toan exemplary embodiment.

FIG. 3 is a schematic diagram of a flow delivery system, according to anexemplary embodiment.

FIG. 4 is a schematic diagram of a flow delivery system, according to anexemplary embodiment.

FIG. 5 is a schematic diagram of a flow delivery system, according to anexemplary embodiment.

FIG. 6 is a schematic diagram of a flow delivery system, according to anexemplary embodiment.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplaryembodiments in detail, it should be understood that the application isnot limited to the details or methodology set forth in the descriptionor illustrated in the figures. It should also be understood that theterminology is for the purpose of description only and should not beregarded as limiting.

Referring generally to the figures, embodiments of the systems andmethods described herein are directed to a real time diagnostic systemfor a mass flow controller. Implementations are directed to flowcontrollers that provide real-time measurements of actual flow whiledelivering and/or controlling the flow of fluids or gases through thesystem. Implementations are directed to techniques that would allow adevice to deliver and control the gas and/or fluid, while simultaneouslymeasuring the amount of flow. Embodiments provide real time monitoringand diagnostic capabilities while the device controls and deliversfluid.

A flow controller may use the pressure in the pipe, temperature of thefluid and either a flow through an orifice or through a known volume tocontrol the flow of a desired amount of fluid by controlling an outletvalve. Measuring the flow includes, but is not limited to, a pressuresensor controlled MFC that relies on the change in pressure across anorifice to deliver gas or other fluids, a device measuring pressure,volume and temperature will be able to also deliver such gas and/orother fluids. Embodiments provide a measuring technique to the abovementioned technique that will measure the amount of fluid flowingthrough the system and provide a further verification to theabove-mentioned implementations. An independent sensing technique todetermine the flow rate through a thermal sensor and/or a flow over aMEMS sensor or a velocity measurement sensor can be used to determineflow through a pipe. Further alarms may be generated based on the inputreceived from independent sensors.

Referring to FIG. 1, FIG. 1 is a schematic diagram of a flow system 1,according to an exemplary embodiment. Flow system 1 includes a mass flowcontroller 5 a, a set point 6, a fluid path 10, an inlet isolation valve20, outlet isolation valve 42, actual flow indicator signal 43, and anindicated flow indicator signal 44.

The fluid delivery path 10 is a hollow tube, pipe or similar channelthat may be composed of a material that are non-reactive to the fluid orgas being delivered from inlet isolation valve 20 to outlet isolationvalve 42. The materials include, but are not limited to, polyurethane,high purity stainless steel, Inconel and haste alloy. The materials maybe non-reactive to various liquids and/or gasses. Materials, such as butnot limited to, haste alloy, Inconel, and/or passivated stainless steelmay be used for fluid delivery path 10. The fluid delivery path 10provides a hollow volume that is used for the transportation of gassesand/or liquids in one or more directions towards outlet isolation valve42. The volume in fluid delivery path 10 can be accurately measured toNIST or other standards. A fluid may be accurately delivered by usingthe results of the volume measurement in conjunction with pressure andtemperature measurements in the fluid delivery path 10 and then thefluid may be precisely controlled by the fluid outlet valve.

Inlet isolation valve 20 controls the flow of the fluid or gas that ispassed through the fluid delivery path 10. Inlet isolation valve 20 maybe a pneumatic valve, high precision piezo type control valve, orsolenoid type of valve. Inlet isolation valve 20 may be configured to benormally open or normally closed. The mass flow controller 5 a may beconfigured to control the inlet isolation valve 20, in one embodiment.In one embodiment, the mass flow controller 5 a may open or close theinlet isolation valve 20 based on a sensor reading from within the massflow controller.

The set point 6 is an input value that is received by the mass flowcontroller 5 a. The value that is received may represent the desiredflow rate that the mass flow controller 5 a should output. The mass flowcontroller 5 a may control the valves that are located within the massflow controller 5 a to output fluids and/or gases to deliver the sameflow rate as the received set point 6 flow rate as accurately aspossible by the system.

The mass flow controller 5 a is configured to receive as input a setpoint 6 and gas and/or fluid enters into the mass flow controller 5 athrough a fluid delivery path 10. The mass flow controller 5 a hasvarious outputs, such as but not limited to, an outlet isolation valve42, an actual flow signal 43, and an indicated flow signal 44. Gasand/or fluid may exit through an output flow path 41. The mass flowcontroller 5 a is configured to set, measure and control the flow of aparticular gas or liquid.

The mass flow controller 5 a includes a primary sensor 22, a secondarysensor 24, a controller 18, a control valve 36 and an orifice 38. Theprimary sensor 22 may be configured to determine the incoming pressureof the fluid that is flowing through the fluid delivery path 10.Pressure sensing technologies deployed could be, but not limited to,diaphragm type, thermistor, resistor, or reactant type. In anotherembodiment, the primary sensor 22 may be a temperature sensor that isused to measure the temperature of the fluid and/or the block of thefluid delivery path 10. In yet another embodiment, the primary sensor 22may be a combination of a pressure and temperature sensors. The primarysensor 22 may generate a signal that allows the controller 18 todetermine the flow rate of control valve 36.

The controller 18 of the mass flow controller 5 a may receive analogelectrical signals from the primary sensor 22. The received signalcurrent or voltage may change based on the pressure and/or temperatureof the gas and/or liquid flowing through the fluid delivery path 10. Thecontroller 18 may include a memory 30, processor 32 and controllermodule 34. The memory 30 is configured to store the received set point 6and store the sensor readings from the primary sensor 22 and secondarysensor 24. The memory 30 may store instructions that may be executed bythe processor 32. The processor 32 may communicate with the memory 30and the controller module 34. The controller module 34 may communicatewith the control valve 36. The communications between the control valve36 and the controller module 34 may include adjusting the flow rate ofthe liquid or gas flowing through the control valve 36. The adjustmentsmay include opening and closing the valve to assure the actual flow 43and the set point 6.

In other embodiments, the mass flow controller 5 a may include asecondary sensor 24. The secondary sensor 24 may include athermal/temperature-based gas measurement sensor, a velocity measurementsensor, MEMS sensor or other techniques, which are independent of theuse of the primary sensor 22. In some embodiments, the secondary sensor22 generates a signal that generates an alarm. The alarm may be userprogrammable such that when the secondary sensor 24 measurements deviateby a certain percentage (e.g., less than or more than 1%, 2%, 3%, 4%,5%, 10%, 15%, 20%, etc.) from previously measured values, then the alarmis triggered and presented to the user of the MFC. As shown in FIG. 1,the secondary sensor may receive a flow of fluid or gas from a bypass 12that shunts a portion of the fluid flow from the fluid flow path to thesecondary sensor 24. The secondary sensor 24 may return the contentsfrom bypass 12 back to the fluid flow path 10 after taking a measurementusing the secondary sensor 24.

In an alternative embodiment, the controller 18 may receive signals fromthe primary sensor 22 and secondary sensor 24 and adjust the controlvalve 36 based at least partially on the sensor readings of both theprimary sensor 22 and the secondary sensor 24. In some embodiments, theprimary sensor 22 may detect the flow and the secondary sensor 24 mayalso detect the flow passing through flow 10. In some embodiments, whenthe flow measured by both sensors differs, the MFC 5 a may determinewhich one or both of the sensors may be malfunctioning. In someembodiments, the sensor that may be malfunctioning may be calibrated toset the sensor value to be equal to the flow received from the othersensor.

The orifice 38 may be optional, in one embodiment, and is typically usedto ensure the fluid delivery is in the sonic regime. The fluid will beinsensitive to up-stream pressure fluctuations by being in the sonicregime.

Referring to FIG. 2a , FIG. 2a illustrates as schematic diagram of amass flow controller 5 b. The inputs and the outputs of the mass flowcontroller 5 b may be similar to the inputs and outputs of the mass flowcontroller 5 a. However, the mass flow controller 5 b comprises three ormore sensors that aid the controller 118 to manage the flow through thefluid delivery path 10.

The mass flow controller 5 b includes an alternate sensor 122, apressure sensor 124, a temperature sensor 126, controller 118, controlvalve 136, and orifice 138. Pressure sensor 124 measures the incomingpressure of the fluid at any given instance. Pressure sensingtechnologies deployed could be, but not limited to, diaphragm,thermistor or resistor type, or reactant type. Temperature sensor 126measures the temperature of the fluid and/or the block of the fluiddelivery path 10. Commercially available sensors such as diaphragm type,thermistor or resistor type can be used in the system.

The orifice 138 is optional in the setup and is typically used to ensurethe fluid delivery is in the sonic regime. Being in the sonic regimeallows for the fluid to be insensitive to up-stream pressurefluctuations.

Alternate sensor 22 is using a thermal-based gas measurement sensor, avelocity measurement sensor, MEMS sensor or other techniques which areindependent of the use of fluid delivery path 10, pressure sensor 24,temperature sensor 26. The alternate sensor 22 generates a signal thatgenerates an alarm, which may be transmitted to the user by indicatedflow 44 or by an independent designated alarm signal. The alarm is userprogrammable such that when the alternate sensor 22 measurements deviateby a certain percentage (e.g., less than or more than 1%, 2%, 3%, 4%,5%, 10%, 15%, 20%, etc.), then the alarm is triggered. In someembodiments, the alternate sensor 22 can be a Coriolis principle sensoror sensors and/or momentum measurement sensor could be an alternatesensor 22 as well.

Control system 118 takes the input from 24, 26 and has the knownmeasured volume 10 in its algorithm. Using the values from the pressuresensor, the temperature sensor and the known volume 10, control system28 can then send an output signal to control valve 28 to adjust itselfto a required control state. Such control state is provided to controlsystem 28 from outside the mass flow controller 5 b as described below.

Control valve 136 is used to control the delivery of gas through thesystem to the desired/required set point/flow-rate. Control valve 136could be a solenoid, piezoactuated or other such high precision controltype valve. Control Valve 136 gets its input from control system 118,and is a function of the values of alternate sensor 122, pressure sensor124, and temperature sensor 126.

Similar to inlet isolation valve 20, outlet isolation valve 42 acts as afinal control step (on/off) between the mass flow controller 5 b and thereaction chamber or the next step where the fluid is delivered. In oneembodiment, the outlet isolation valve 42 may have the same constructionas inlet isolation valve 20. In another embodiment, the inlet isolationvalve 20 and the outlet isolation valve, outlet isolation valve 42 maybe different type of values. In this embodiment having two differenttypes of values allows a user to diagnose a problem with a value typeverses another valve type.

Mass Flow controller 5 b may comprise all or some of the elementsmentioned above. The controller 118 calculates the position of thecontroller valve 136 based on the signals received from the alternatesensor 122, the pressure sensor 124, and the temperature sensor 126. Thecontroller 118 attempts to maintain actual flow 43 to be equal to theset point 6. While controller 118 performing the above operations,alternate sensor 22, being an independent and self-contained measurementsystem, is configured to measure the flow through flow path 10 andprovide the measured value to control system 118. Control system 118 hasthe ability to provide the value calculated from alternate sensor 122,relative to the calculated flow based on measuring the values fromalternate sensor 122, pressure sensor 124, temperature sensor 126 andthe position of valve 136. This value could be provided as an absoluteflow value, or provided as a calculated relative error to set point, orrelative error to expected flow. Mass flow controller 5 b recordsvarious key parameters (e.g. actual flow, expected flow, temperature,etc.) over a user-settable period of time on memory 30. Such parametersare, but are not limited to set point 6, actual flow 43 from alternatesensor 22, expected flow calculated by 118 based on pressure sensor 24,temperature 26 and control valve 136 position and so on.

Referring to FIG. 2b , FIG. 2b illustrates a flow system according toanother embodiment. The system in FIG. 2b is similar to the systems inFIGS. 1 and 2 a. However, in FIG. 2b the alternate sensor 122 is locatedwithin the fluid flow path after the orifice 138 and before the outletisolation valve 42. As shown in FIG. 2b , the alternate sensor 122 mayreceive a flow of fluid or gas from a bypass 12 that shunts a portion ofthe fluid flow from the fluid flow path to the alternate sensor 122. Thealternate sensor 122 may return the contents from bypass 12 back to thefluid flow path 10 after taking a measurement using the alternate sensor122. The alternate sensor 122 generates a signal that represents therelative fluid flow through the bypass 12 to the controller 118. Thecontroller 118 retrieves information stored in the memory 130 andgenerates an indicated flow 44. In some embodiments, the actual flow 43and indicated flow 44 may be compared to generate an additional signalrepresenting an alarm condition. The alarm signal is generated when theactual flow 43 and indicated flow 44 have a predetermined difference. Insome embodiments, when the actual flow 43 and the indicated flow 44differ by more than or less than 1, 2, 3, 4, 5, 10, 15, 20 percent analarm is generated.

FIG. 3 illustrates a flow system according to another embodiment. Thesystem in FIG. 3 is similar to the systems in FIGS. 1 and 2 a-b. FIG. 3shows the mass flow controller 5 c that includes an ultrasonic sensor228. However, instead of using a pressure sensor 124 and/or atemperature sensor 126, an ultrasonic sensor 228 may replace bothsensors. The controller 218 controls the control valve 236 by using thesensor readings from the ultrasonic sensor 228. In various embodiments,the ultrasonic sensor 228 may include providing the pressure and thetemperature to the controller 218. In some embodiment, the mass flowcontroller 5 c may include the alternate sensor 122 from FIG. 2. Inanother embodiment, the mass flow controller 5 c may include thesecondary sensor 24 from FIG. 1. In yet another implementation, the massflow controller 5 c may include both alternate sensor 122 and thesecondary sensor 24.

FIG. 4 illustrates a mass flow controller 5 d. In various embodiments,the mass flow controller 5 d, receives as input the fluid delivery path10, and set point 6. The mass flow controller 5 d may output the outputflow path 41. Mass flow controller 5 d includes various components aresimilar to the components of mass flow controllers 5 a-5 c. Inparticular, mass flow controller 5 d includes, an alternate sensor 510,pressure sensor 512, temperature sensor 514, a controller 516, an outputisolation valve 524, an alternate sensor 526 and an orifice 527.

The alternate sensor 510, pressure sensor 512, and temperature sensor514 may act in a similar manner as alternate sensor 122, pressure sensor124 and temperature sensor 126 as discussed above with respect to FIG.2. As shown in FIG. 4, the output isolation valve 524 may be connectedto an alternate sensor 526 that includes a bypass shunt similar toalternative sensor 510. In other embodiments, the alternate sensor 526may in an inline sensor similar to the pressure and/or temperaturesensors. The alternate sensor 526 may generate a signal and provide itto the controller 516. The controller 516 may adjust the flow throughthe fluid delivery path 10 using the output isolation valve 524. In someembodiments, the controller 516 may adjust the actual flow 43 and/orindicated flow 44 based on the output of the alternate sensor 526.

The output from the alternative sensor 526 may be connected to theorifice 527 and the fluid delivery path 10 may be output as the outputflow path 41 via valve 42 that is located outside the mass flowcontroller. In some embodiments, the valve 42 may be located within themass flow controller 5 a-d.

In other embodiments, the alternate sensor 510 or 526 may be a velocitysensor or a thermal sensor. In some embodiments, the alternate sensor510 and 526 may be thermal sensors. In various implementations, avelocity sensor may replace the pressure sensor 512 and/or thetemperature sensor 514. In other embodiments, the order of the sensorsmay be interchangeable. For example, the temperature sensor may belocated first in the mass flow controller 5 a-d. The temperature sensormay be followed by a pressure sensor, which is followed by an alternatesensor. In other embodiments, the alternate sensor may be locatedbetween the pressure and the temperature sensors.

FIG. 5 illustrates mass flow controller system according to anotherembodiment. Due to the fact that sensors or fluid control line may failat a greater rate than the controller electronics, the controller may beremovably attachable to the mass flow controller. As shown in FIG. 5 themass flow controller 5 e may comprise a sensor portion 610 and acontroller portion 618. The controller portion 618 may receive varioussignals from the sensor portion 610 a and the sensor portion 610 a mayreceive various signals from the controller portion 618. In someembodiments, when the controller portion 618 determines that the sensorportion 610 a is failing, the controller portion 618 may generate analarm so that the sensor portion 610 a may be swapped out or replacedwith a new sensor portion. Each sensor portion includes a memory that isconfigured to store, for example, the volume that is between the inputisolation value 20 and the output isolation valve 620. The controller618 may access the memory in the sensor portion to determine the volumewithin the mass flow controller.

The new sensor portion may include a memory 518 b or 518 c that isconfigured to store the volume that is between the input isolation valve20 and the output isolation valve 620. The controller 618 may access thememory 626 in the sensor portion to ascertain the volume within the massflow controller. The volume allows the mass flow controller toaccurately calculate the flow of gas and/or liquid.

In another embodiment, the controller 618 may be configured to controlmore than one sensor portions as shown in FIG. 5. As shown in FIG. 5 asecond sensor portion 610 b may include similar sensors as sensorportion 610 a and may operate in parallel to sensor portion 610 a. Thecontroller 618 is configured to generate an actual flow 43 and anindicated flow 44 that combines the output from both sensor portions 610a and 610 b. Although two sensor portions as shown in FIG. 5,embodiments of the present disclosure are not limited to having twoparallel sensor portions, instead, the embodiments may include aplurality of sensor portions and/or a plurality of control portions thatoperate in parallel or series.

FIG. 6 illustrates a mass flow controller system according to anotherembodiment. FIG. 6 shows a mass flow controller 5 f, a set point 6, afluid path 10, a fluid path 10, an inlet isolation valve 20, an actualflow 43, indicated flow 44, indicated flow 45, alternate sensor 526,flow path 41 and outlet isolation valve 42. In some respects, the masscontroller 5 f is similar to the mass flow controllers 5 a-5 e. Forexample, the control value 524 is located after the alternate sensor510, the pressure sensor 512 and the temperature sensor 514 havemeasured the fluid flow. Accordingly, the measurements from thealternate sensor 510, the pressure sensor 512 and the temperature sensor514 are calculated and the control valve 524 may be adjusted based onthe readings for at least one of the sensors. The controller 516 maydetermine the actual flow 43 and the indicated flow 44 based on thesensor reading. The control valve 524 is located in the flow path 10between the inlet isolation valve 20 and the orifice 527. In alternativeembodiments, the control valve 524 may be located after the orifice 527or the orifice 527 may be located between the control valve 524 and theinlet isolation valve 20.

The mass flow controller system on FIG. 6 also includes an additionalalternate sensor 526 that measures the output that is received from themass flow controller 5 f. The additional alternate sensor 526 mayindicate to the user of the mass flow controller 5 f whether liquid orgas is flowing through the mass flow controller. The alternate sensor526 may generate an additional indicated flow signal 45 that may becompared with the indicated flow 44 and/or the actual flow 43. In oneembodiment, the signal from the alternate sensor 526 may be used tocontrol the control valve 524. Other uses for the signal from thealternate sensor 526 may be possible.

FIGS. 1-6 show a device comprising of a flow measurement system and aflow controlling system. Flow controlling system has thermal sensor,temperature sensor, pressure sensor, control valve, orifice and PCBA.The flow measurement system has MEMS, thermal, velocity, momentummeasurement and ultrasonic or others. Flow measurement sensor generatesone or more signals that compares against the output of the flowcontroller system and compares against the set point. If the comparisonis out of a user-defined limit, it will send an alarm or a fault to theuser. The user can then decide if the user wants to replace the unit orcheck against an in-situ verification system. Variation of differentapplications according to FIGS. 1-6. The alternate sensor may be locatedoutside of the system (FIG. 6 or 7) and can be installed independentlyanywhere in the flow path outside the existing flow controller. Themomentum sensor may also be used as the primary or the alternate sensorfor either the flow controller or the flow measurement system. (See.,FIGS. 1-6)

This technique is beneficial to the user because existing flowcontrolling system do not provide real-time actual flow measurementinformation. They only report what the sensed flow according to thesensing technique they are using. This handicaps the user because theuser may not know during this process, if the existing flow controllerwas actually flowing correctly or after a few process steps, the usermay get defective or different flow rates. Providing an alternatesensing technique offers the user secondary insurance that will limithow many bad products are made once the flow controlling system has goneout of specification or set point.

The construction and arrangement of the systems and methods as shown inthe various exemplary embodiments are illustrative only. Although only afew embodiments have been described in detail in this disclosure, manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, colors,orientations, etc.). For example, the position of elements may bereversed or otherwise varied and the nature or number of discreteelements or positions may be altered or varied. Accordingly, all suchmodifications are intended to be included within the scope of thepresent disclosure. The order or sequence of any process or method stepsmay be varied or re-sequenced according to alternative embodiments.Other substitutions, modifications, changes, and omissions may be madein the design, operating conditions and arrangement of the exemplaryembodiments without departing from the scope of the present disclosure.

The present disclosure contemplates methods, systems and programproducts on any machine-readable media for accomplishing variousoperations. The embodiments of the present disclosure may be implementedusing existing computer processors, or by a special purpose computerprocessor for an appropriate system, incorporated for this or anotherpurpose, or by a hardwired system, or a printer circuit board.Embodiments within the scope of the present disclosure include programproducts comprising machine readable media for carrying or havingmachine-executable instructions or data structures stored thereon. Suchmachine-readable media can be any available media that can be accessedby a general purpose or special purpose computer or another machine witha processor. By way of example, such machine-readable media can compriseRAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any other mediumwhich can be used to carry or store desired program code in the form ofmachine-executable instructions or data structures and which can beaccessed by a general purpose or special purpose computer or anothermachine with a processor. When information is transferred or providedover a network or another communications connection (either hardwired,wireless, or a combination of hardwired or wireless) to a machine, themachine properly views the connection as a machine-readable medium.Thus, any such connection is properly termed a machine readable medium.Combinations of the above are also included within the scope ofmachine-readable media. Machine-executable instructions include, forexample, instructions and data which cause a general purpose computer,special purpose computer, or special purpose processing machines toperform a certain function or group of functions.

Although the figures may show a specific order of method steps, theorder of the steps may differ from what is depicted. Also two or moresteps may be performed concurrently or with partial concurrence. Suchvariation will depend on the software and hardware systems chosen and ondesigner choice. All such variations are within the scope of thedisclosure. Likewise, software implementations could be accomplishedwith standard programming techniques with rule based logic and otherlogic to accomplish the various connection steps, processing steps,comparison steps and decision steps.

1. A device, comprising: a primary sensor and a secondary sensor locatedalong a flow path within a flow device; the primary sensor and thesecond sensor configured to generate a signal that is indicative of aflow rate of material through the flow path; an outside sensor locatedoutside the flow device to measure the flow of material received fromthe flow device; and the flow device configured to compare a signal fromthe outside sensor with the signal from the primary or secondary sensorto determine that at least one of the primary or secondary sensor ismalfunctioning.
 2. The device of claim 1, wherein the flow device isconfigured to generate at least one signal based on a difference in flowrate between an actual flow rate determined by the outside sensor andthe signal generated by the primary or the secondary sensor.
 3. Thedevice of claim 2, wherein the flow device is configured to generate analarm signal that the actual flow rate and the indicated flow rate areout of preset parameter boundary.
 4. The device of claim 1, wherein thesecondary sensor is a temperature sensor that is configured to measure achange in temperature of the material flowing through the flow path. 5.The device of claim 4, wherein the primary sensor is a pressure sensorthat is configured to measure a change in pressure of the materialflowing through the flow path.
 6. A method for controlling a mass flowcontroller, comprising: generating signals that are indicative of a flowrate of material through the flow path using a primary sensor and asecondary sensor; measuring the flow of material received from the flowpath using an outside sensor; and comparing a signal from the outsidesensor with the signal from the primary or secondary sensor anddetermining that at least one of the primary or secondary sensors ismalfunctioning.
 7. The method of claim 6, further comprising, generatingat least one signal based on a difference in flow rates between anactual flow rate determined by the outside sensor and the signalgenerated by the primary or the secondary sensor.
 8. The method of claim6, further comprising, generating by the mass flow controller, an alarmsignal that the actual flow rate and the indicated flow rates are out ofpreset parameter boundary.
 9. The method of claim 6, wherein thesecondary sensor is a temperature sensor that is measuring a change intemperature of the material flowing through the flow path.
 10. Themethod of claim 6, wherein the primary sensor is a pressure sensor thatis measuring a change in pressure of the material flowing through theflow path.
 11. An apparatus, comprising: a primary sensor means and asecondary sensor means for generating a signal that is indicative of aflow rate of material through the flow path; an outside sensor means formeasuring the flow of material received from the flow path; and a massflow controller means for comparing a signal from the outside sensormeans with the signals from the primary sensor means or secondary sensormeans to determine that at least one of the primary or secondary sensormeans is malfunctioning.
 12. The apparatus of claim 11, wherein the massflow controller means for generating at least one signal is based on adifference in flow rates between an actual flow rate and an indicatedflow rate.
 13. The apparatus of claim 11, wherein the mass flowcontroller means is generating an alarm signal that the actual flow rateand the indicated flow rates are out of preset parameter boundary. 14.The apparatus of claim 11, wherein the secondary sensor means is atemperature sensor that is configured to measure a change in temperatureof the material flowing through the flow path.
 15. The apparatus ofclaim 11, wherein the primary sensor means is a pressure sensor that isconfigured to measure a change in pressure of the material flowingthrough the flow path.